EtherChannel - Understanding LACP port and system priorities

When configuring EtherChannel on Cisco devices using LACP as the negotiation protocol, there are some priority parameters that can be set. These are:

• System Priority: Every switch utilizing LACP must be assigned a system priority, which can be set either automatically or manually via the CLI. The switch combines the system priority with its MAC address to generate the system ID. The switch with the lowest system priority is allowed to make decisions about what ports actively participate in EtherChannel.
• Port Priority: Each switch port must also have a port priority, which can be configured automatically or through the CLI. The port priority, together with the port number, forms the port identifier. The switch uses this priority to determine which ports should be placed in standby when hardware limitations prevent all compatible ports from being aggregated.

Links:

https://forum.networklessons.com/t/troubleshooting-etherchannel/1186/28?u=lagapidis

https://networklessons.com/switching/etherchannel-cisco-ios-catalyst-switch

https://www.ciscopress.com/articles/article.asp?p=2348266&seqNum=3